/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.iotdb.db.metadata.tagSchemaRegion.tagIndex.wal;

import org.apache.iotdb.db.metadata.tagSchemaRegion.tagIndex.Request.DeletionRequest;
import org.apache.iotdb.db.metadata.tagSchemaRegion.tagIndex.Request.InsertionRequest;
import org.apache.iotdb.lsm.request.IRequest;
import org.apache.iotdb.lsm.wal.IWALRecord;
import org.apache.iotdb.lsm.wal.WALReader;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;

/**
 * Manage wal entry writes and reads
 */
public class WALManager extends org.apache.iotdb.lsm.manager.WALManager {

    private static final Logger logger = LoggerFactory.getLogger(WALManager.class);

    private static final int INSERT = 1;

    private static final int DELETE = 2;

    public WALManager(
            String schemaDirPath,
            String walFileName,
            int walBufferSize,
            IWALRecord walRecord,
            boolean forceEachWrite)
            throws IOException {
        super(schemaDirPath, walFileName, walBufferSize, walRecord, forceEachWrite);
    }

    public WALManager(String schemaDirPath) {
        super(schemaDirPath);
    }

    /**
     * handle wal log writes for each request context
     *
     * @param request request context
     * @throws IOException
     */
    @Override
    public synchronized void write(IRequest request) {
        if (isRecover()) return;
        try {
            switch (request.getRequestType()) {
                case INSERT:
                    process((InsertionRequest) request);
                    break;
                case DELETE:
                    process((DeletionRequest) request);
                    break;
                default:
                    break;
            }
        } catch (IOException e) {
            logger.error(e.getMessage());
        }
    }

    /**
     * for recover
     *
     * @return request context
     */
    @Override
    public synchronized IRequest read() {
        WALReader walReader = getWalReader();
        if (walReader.hasNext()) {
            WALEntry walEntry = (WALEntry) getWalReader().next();
            if (walEntry.getType() == INSERT) {
                return generateInsertRequest(walEntry);
            }
            if (walEntry.getType() == DELETE) {
                return generateDeleteContext(walEntry);
            }
        }
        return null;
    }

    /**
     * generate insert context from wal entry
     *
     * @param walEntry wal entry
     * @return insert context
     */
    private InsertionRequest generateInsertRequest(WALEntry walEntry) {
        return new InsertionRequest(walEntry.getKeys(), walEntry.getDeviceID());
    }

    /**
     * generate delete context from wal entry
     *
     * @param walEntry wal entry
     * @return delete context
     */
    private DeletionRequest generateDeleteContext(WALEntry walEntry) {
        return new DeletionRequest(walEntry.getKeys(), walEntry.getDeviceID());
    }

    /**
     * handle wal log writes for each insert context
     *
     * @param request insert request
     * @throws IOException
     */
    private void process(InsertionRequest request) throws IOException {
        WALEntry walEntry = new WALEntry(INSERT, request.getKeys(), request.getValue());
        getWalWriter().write(walEntry);
    }

    /**
     * handle wal log writes for each delete context
     *
     * @param request delete context
     * @throws IOException
     */
    private void process(DeletionRequest request) throws IOException {
        WALEntry walEntry = new WALEntry(DELETE, request.getKeys(), request.getValue());
        getWalWriter().write(walEntry);
    }
}
